R help - Sep 2008 - creating baseline variable from a longitudinal sequence

Dear R-help mailing list,
 
Kindly help me out with this problem:
 
I have a dataset that is in the format below,
ID  time  Y  Age
1  0     195  23.1
1  2    204  23.3
1  4   202    23.5
2  0  170    22.0
2  3   234   22.2
3  0  208   24.4
3  2  194  24 .7
3  3   204  24.9
 
I wish to remove all the measurements at time point 0 and convert them to a
baseline variable as follows;
 
 ID  time  Y  Age  baseline
1  2    204  23.3   195
1  4   202    23.5   195
2  3   234   22.2    170
3  2  194  24 .7     208
3  3   204  24.9     208
 
Thanks.
 
regards
John 
 
 


      
	[[alternative HTML version deleted]]

john james wrote:
> Dear R-help mailing list,
> ?
> Kindly help me out with this problem:
> ?
> I have a dataset that is in the format below,
> ID? time? Y? Age
> 1? 0???? 195? 23.1
> 1? 2??? 204? 23.3
> 1? 4?? 202??? 23.5
> 2? 0? 170??? 22.0
> 2? 3?? 234?? 22.2
> 3? 0? 208?? 24.4
> 3? 2? 194? 24 .7
> 3? 3?? 204? 24.9
> ?
> I wish to remove all the measurements at time point 0 and convert?them to a
baseline variable as follows;
> ?
> ?ID? time? Y? Age? baseline
> 1? 2??? 204? 23.3?? 195
> 1? 4?? 202??? 23.5?? 195
> 2? 3?? 234?? 22.2??? 170
> 3? 2? 194? 24 .7???? 208
> 3? 3?? 204? 24.9???? 208
>   
Something in your mail path (or mine) is inserting funny characters in
your text, making it a bit hard to use the data for testing...

Anyways, I'd split the data frame into the baseline values and the rest
using subset() or maybe split(), rename the baseline variable(s) and
then stick things together with merge()

-- 
   O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907

If DF is your data.frame:

subset(cbind(DF, baseline=rep(DF$Y[DF$time == 0], table(DF$ID))), time > 0)

On Tue, Sep 16, 2008 at 11:01 AM, john james <dntssa@yahoo.com> wrote:
> Dear R-help mailing list,
>
> Kindly help me out with this problem:
>
> I have a dataset that is in the format below,
> ID  time  Y  Age
> 1  0     195  23.1
> 1  2    204  23.3
> 1  4   202    23.5
> 2  0  170    22.0
> 2  3   234   22.2
> 3  0  208   24.4
> 3  2  194  24 .7
> 3  3   204  24.9
>
> I wish to remove all the measurements at time point 0 and convert them to a
> baseline variable as follows;
>
>  ID  time  Y  Age  baseline
> 1  2    204  23.3   195
> 1  4   202    23.5   195
> 2  3   234   22.2    170
> 3  2  194  24 .7     208
> 3  3   204  24.9     208
>
> Thanks.
>
> regards
> John
>
>
>
>
>
>        [[alternative HTML version deleted]]
>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

	[[alternative HTML version deleted]]